Apparatus for roll forming strip material



June 10, 1941. 4 ,J N 2,245,407

' APPARATUS FOR ROLL FORMING STRIP MATERIAL Filed Sept. 2, 1938 2 Sheets-Sheet 1 lNVENT-OR dm/v L/a/vm/v ATTORNEY June 10, 1941. I J. A. LIGNIAN 2,245,407

1 APPARATUS FOR ROLL FORMING STRIP HATERIAL 2 Sheets-Sheet 2 Filed Sept. 2, 1938 V INVENTOR u'sn/v f1 L/s/wn/v BY W mmnlt A ATTORNEY Patented June 10, 1941 APPARATUS WOR ROLL FORMING S'iRIP MATERIAL Jean A. Lignian, Dayton, Ohio, aslignor. to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application September-'2, 1935, Serial No. 228,142

' Claims.

This invention relates to an apparatus for roll forming strip stock and is particularly concerned with roll forming semi-cylindrical bearings and the like from flat stock.

An object of the invention is to provide a method for roll forming strip stock wherein pressure is applied perpendicular to the plane of the strip adjacent the leading and tail edges thereof during the roll forming operation on the stock, thereby causing the formed strip to have a constant radius throughout.

A further object of the invention is to provide a method of roll forming strip'stock wherein the flat spots heretofore present at the leading and tail edges of the strip are eliminated, and the strip is formed in a true arcuate shape throughout.

A still further object of the invention is to provide a method for roll forming flat stock wherein the stock is passed between cooperating ,roll forming elements and is pinched or squeezed at the leading and tail edges thereof while the remainder of the strip is roll formed, thereby causing the formed stock to be of the desired shape throughout.

Another object of the invention is to provide a method as defined in the preceding object in which the strip is ejected from between the roll forming elements after the same is formed to the desired shape.

In carrying out the preceding objects it is a further object in some cases to release the pressure on the formed strip when the same is between the roll forming elements, so that the strip may be readily removed.

ment of the present invention is clearly shown.

In the drawings: Fig. 1 illustrates one type of roll forming equipment and shows the strip stock just prior A further object of the invention is to provide an apparatus for carrying out the hereindescribed method, said apparatus comprising a shiftable roll which is normally yieldably biased toward one side of a cooperating die element, said roll being shifted with respect to the die as the strip stock is inserted therebetween, the bias on said roll creating the pressures heretofore defined.

} In carrying out the above object it is a further object to provide external loading means for creating the yieldable bias on said roll.

Another object, in some cases, is to provide spring loaded rollers for acting upon the we I ternal surface of said shiftable roll for biasing said shiftable roll toward said di Further objects and advantages of the present invention will be apparent'from the following description, reference being had to the accompanying drawings wherein a preferred embodithan to its entry between the roll forming elements. Fig. 2 is a view similar to Fig. l in which the strip stock has just been inserted between the roll forming elements.

Fig. 3 is a view similar to Fig. 1 with the stri in the partially formed condition, and

Fig. 4 is a view similar to Fig. 1 showing the strip in the completely formed condition.

, When roll forming strip material, for example in the manufacture of cylindrical bearing blanks and the like, there has always been a tendency for the formed strip to have flat spots adjacent .'the leading and tail edges thereof. In other words theformed strip has never been a true semi-cylindrical shape, having a constant radius throughout, unless subsequent operations are carried out on the strip after it has been roll formed. This may be explained by the fact that die, it has always been necessary to include a finishing operation to eflect a true semi-cylindrical bearing. One of such finishing operations comprises rolling a bearing into slightly greater than 180 are and then trimming off the two ends thereof, thereby'eliminating the fiat spots and obtaining a semi-cylindrical bearing of 180" arc. Another method of effecting a similar result is to roll the bearing in a slightly greater arc and then place the same in a die and strike the fiat endsof the bearing to coin the same slightly. Either of theseexpediencies are expensive and require additional handling and are therefore objectionable from a production standpoint.

The present invention is directed to a method and apparatus for eliminating these problems wherein a method and apparatus is proposed which produces semi-cylindrical bearings to the correct size and having a constant radius throughout. The usual roll forming equipment is modified so that the roll is shiftable relative In'the manufacture of semi-"* to the die and is yieldably loaded so as to create high pressures upon the strip at its point of entry between the roll and die. In other words the strip is pinched or squeezed in a plane perpendicular thereto at the leading edge thereof for causing the strip to curl adjacent the leading edge thereof and conform substantially to the shape of the roll. As the strip progresses between the die and roller elements pressure is progressively applied to roll the blanks to semicylindrical shape. Due to the external loading on the roll, the tail edge of the strip is likewise compressed or squeezed so as to substantially conform to the shape of the roll. Thus, due to the external loading on the roll and the pressure exerted by the same adjacent the leading and tail edges of the strip, the flat spots adjacent the edges thereof are eliminated, and-the formed bearing is substantially constant in radius throughout.

Referring to the drawings, the progression of the strip through the dies is clearly shown and it is visually apparent that the shiftable roll changes in position according to the position of the strip stock therein. In the present embodiv ment 20 illustrates a die block having a semiinch to .250 of an inch in thickness that a clearance of from .010 to .020 is suflicientto give the desired result. In the present instance a plurality of rollers 30 and 3| are provided which bear on the outer periphery of the roll 24. The rollers 30 and 3| are spring loaded by means of springs 32 so as to yieldably hold the roll 24 in th position shown in Fig. l'when there is no strip stock between the roll and the die. The rollers 38 and 3| may be adjusted so that their positions with respect to roll 24 can be varied so as to produce the desired result. In practice it has been found that the position of roll 38 should be as close to the vertical axis A of roll 24 as possible, and that the roll 3i should be positioned adjacent the axis B. It is manifest that other means can be utilized to produce loading on roll 24 such as external loading means acting on the axis of the roll in which case the clearance between the bearing and the axis need be very slight since the axis itself is 'shiftable.

A magazine feed device 34 is provided for holding a number of bearing blanks 36. The device 34 includes a reciprocating plunger 38 and the magazine of blanks 36 which are either spring pressed against the plunger or are 'fed thereto by gravity. Thus upon each reciprocation of plunger 38, a blank 36 is forced between roller 24 and die surface 22. In order to remove the formed bearing blanks between the roller and the die a plurality of ejector pins 40 are provided in a lateral wall in a die cavity 22. The pins may be operated by a cam mechanism so that upon each upward movement of the plunger 38 the pins move outwardly to eject the formed hearing from between the roll and die. If desired, additiorfai cam mechanism may be employed to remove the loading from the roller 24 at the instant of ejection.

Following through'the steps of the method as shown in the drawings and referring particularly to Fig. 1, a bearing blank 36 is shown just prior to its entry between the roller and the die. At this instant the roller is moved toward one side of the die cavity and spring loaded rollers 38 and 3| exert a resultant force as shown as C with a vertical component of force acting on line D and a horizontal component of force acting on line E. As the plunger 38 moves the strip to the position shown in Fig. 2 th strip is squeezed between the roll and the die adjacent the leading edge thereof, and displaces the roll upwardly against the compression of the springs 32. Obviously the compressing force against the strip tending to .sequeeze the end thereof is the component force D acting perpendicular to the plane of the strip. Further movement of the plunger 38 causes the strip to assume the position'shown in Fig. 3 wherein pressure is being applied progressively to the strip as the same passes between the roll and the die. After the leading edge of the strip passes the horizontal axis of roll 24, the spring loaded rollers II and 32 have substantially no further effect upon that portion of the strip.

Fig. 4 shows the strip in its completely formed condition with the plunger 38 at its innermost point. The roll 24 is centered within the .die cavity and it will be noted that the roll 24 is compressing the tail edge of the strip with a force equal to component D, and acting perpendicular to the plane of the strip. Thus the strip has been compressed adjacent the leading edge thereof, progressively compressed and rolled to shape as it passes between the roll and die and finally compressed adjacent the tail edge thereof to completely shape the entire length of strip in arcuate form having a constant radius throughout. 4

The ejector pins 40 are mechanically connected with the feeding mechanism and, when the strip assumes the position shown in Fig. 4, I

act laterally against the edge thereof to press the strip from between the roll and die.

It is apparent that many varied types of apparatuses could be used to accomplish similar results, and such apparatus modifications are fully within the scope of the present invention, the invention residing in the compression and shaping of the leading and tail edges of the bearing blanks as the same are being shaped so as to conform the entire bearing blank to a true semi-cylindrical shape. It is also manifest that the use of the present invention is not limited to the manufacture of any arcuate section of metal.

It has been found that after ejection or removal of th bearing from between the roll forming elements that the bearing has a certain amount of spring depending upon the thickness of the stock. Therefore, when using the apparatus and the method disclosed herein, the diameter of the roll and the radius of the die cavity should be calculated so as to produce the desired size of bearing. Thus with a roll formed bearing the stresses and strains introduced in the metal are equalized due to the progressive forming of th bearing and the formed bearing is true in radius. In other methods heretofore mentioned the strains are not so equalized and the bearing upon removal from the die may spring to the shape of an elliptical arc.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms a spaced distance from said die element at all might be adapted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. An apparatus for roll forming strip stock comprising in combination, a die having a curved surface cavity therein, a cooperating roller loosely journaled 'upon a fixed axle and disposed so that at least a portion of the same is within said cavity, said axle being so disposed with respect to the cavity that said roller is spaced from the cavity wall at all times, said roller being shiftable with respect to its journal and to the axis of said cavity, and a plurality of external loading means acting upon said roller for yieldably urging the same toward one side of said cavity whereby said roller is progressively shifted to differentpositions with respect to its axle when strip stock is inserted and advanced between the roller and the wall of the die cavity.

2. The apparatus defined in claim 1 in which a reciprocating plunger is utilized to force the strip stock between the roller and the die.

3. The apparatus defined in claim 1 wherein ejecting means are provided for ejecting the formed strip from between the roller and the die.

4. An apparatus for forming strip stock to an arcuate shape, comprising in combination; an immovable semicircular die element, a floating roll loosely journaled upon a fixed axle and held desired shape;

times, external loading means acting upon the outer surface of said roll for yieldably urging the roll toward the element, means for forcing strip stock between the roll and the element whereby the roll is shifted with respect to its axle, said last means advancing the strip between the roll .and die element for progressively changing the position of the roll with respect to its axle and simultaneously forming the strip stock to the 5. An apparatus for forming strip stock to an arcuate shape, comprising in combination; an immovable semicircular die element, a floating roll loosely journaled upon a fixed axle and held a spaced distance from said die element at all times, external loading means acting upon the outer surface of said roll for yieldably urging the roll toward the element, means for forcing strip stock between the roll and the element whereby the roll is shifted with respect to its axle, said last means advancing the strip between the roll and die element for progressively changing the position of the roll with respect to its axle and simultaneously forming the strip stock to the desired shape, and a plurality of pins acting laterally in the space between the roll and the die element for ejecting the formed strip therefrom.

JEAN A. LIGNIAN. 

